kern: dev: Add initial console driver

This commit introduces the boot console driver and integrates it with
the tracing system

Signed-off-by: Ian Moffett <ian@osmora.org>

1 files changed, 165 insertions, 0 deletions

diff --git a/sys/dev/cons/cons.c b/sys/dev/cons/cons.c
new file mode 100644
index 0000000..706e1b0
--- /dev/null
+++ b/sys/dev/cons/cons.c
@@ -0,0 +1,165 @@
+/*
+ * Copyright (c) 2025 Ian Marco Moffett and the Osmora Team.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of Hyra nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <sys/errno.h>
+#include <sys/types.h>
+#include <sys/param.h>
+#include <lib/string.h>
+#include <dev/cons/font.h>
+#include <dev/cons/cons.h>
+
+#define DEFAULT_FG 0x808080
+#define DEFAULT_BG 0x000000
+
+/*
+ * Render a character to the screen
+ */
+static void
+cons_blit_ch(struct console *cons, uint32_t x, uint32_t y, char c)
+{
+    struct vram_dev *vram;
+    size_t idx;
+    uint8_t *glyph;
+    uint32_t fg, bg;
+
+    vram = &cons->vram;
+    glyph = &g_CONS_FONT[(int)c*16];
+
+    fg = cons->fg;
+    bg = cons->bg;
+
+    for (uint32_t cy = 0; cy < FONT_HEIGHT; ++cy) {
+        idx = vram_index(vram, x + (FONT_WIDTH - 1), y + cy);
+        for (uint32_t cx = 0; cx < FONT_WIDTH; ++cx) {
+            vram->io[idx--] = ISSET(glyph[cy], BIT(cx)) ? fg : bg;
+        }
+    }
+}
+
+/*
+ * Clear the console to its background color
+ */
+static void
+cons_clear(struct console *cons)
+{
+    struct vram_dev *vram;
+
+    vram = &cons->vram;
+    if (vram->io == NULL) {
+        return;
+    }
+
+    memset(vram->io, cons->bg, vram->pitch * vram->height);
+}
+
+/*
+ * Print a newline to the console
+ */
+static void
+cons_newline(struct console *cons)
+{
+    struct vram_dev *vram;
+
+    vram = &cons->vram;
+    cons->ty += FONT_HEIGHT;
+    cons->tx = 0;
+    if (cons->ty >= vram->height - FONT_HEIGHT) {
+        cons->tx = 0;
+        cons->ty = 0;
+        cons_clear(cons);
+    }
+}
+
+/*
+ * Handle a special character
+ *
+ * Returns the character given if it is a special
+ * character, otherwise -1
+ */
+static int
+cons_special(struct console *cons, char c)
+{
+    switch (c) {
+    case '\n':
+        cons_newline(cons);
+        return c;
+    }
+
+    return -1;
+}
+
+/*
+ * Write a single character to the console
+ */
+static void
+console_putch(struct console *cons, char c)
+{
+    struct vram_dev *vram;
+
+    if (cons_special(cons, c) == c) {
+        return;
+    }
+
+    vram = &cons->vram;
+    cons_blit_ch(cons, cons->tx, cons->ty, c);
+    cons->tx += FONT_WIDTH;
+    if (cons->tx >= vram->width - FONT_WIDTH) {
+        cons_newline(cons);
+    }
+}
+
+int
+console_write(struct console *cons, const char *s, size_t len)
+{
+    for (size_t i = 0; i < len; ++i) {
+        console_putch(cons, *s++);
+    }
+}
+
+int
+console_reset(struct console *cons)
+{
+    int error;
+
+    if (cons == NULL) {
+        return -EINVAL;
+    }
+
+    /* Try to acquire the VRAM descriptor */
+    if ((error = vram_getdev(&cons->vram)) < 0) {
+        return error;
+    }
+
+    cons->fg = DEFAULT_FG;
+    cons->bg = DEFAULT_BG;
+    cons->tx = 0;
+    cons->ty = 0;
+    cons->active = 1;
+    return 0;
+}